Expandable suspension system for loudspeaker bobbin

ABSTRACT

The suspension wires extending tangentially to the outer periphery of the coil bobbin positioned within a cylindrical air gap of the magnetic circuit of a loudspeaker defined by the magnetic plate forming a portion of that circuit and the pole, include an integral wire coil portion permitting expansion and contraction in the direction of the wire axis. A viscous damper may be applied to the wire adjacent the coil intermediate the coil and the bobbin and may bridge the wire and the fixed magnetic plate.

United States Patent [191 Kinoshita 1 Mar. 11, 1975 EXPANDABLE SUSPENSION SYSTEM FOR LOUDSPEAKER BOBBIN [75] lnventor: Showzo Kinoshita,Tokorozawa,

Japan [73]- Assignee: Pioneer Electronic Corporation, Tokyo, Japan [22] Filed: May 23, 1973 [21] Appl. No.: 362,983

130] Foreign Application Priority Data June 20, 1972 Japan 47-72181 [52] US. Cl 179/115.5 VC, 179/180.

[51] Int. Cl. H041 9/04 [58] Field of Search l79/115.5 R, 115.5 VC, 179/180; 181/32 R,166, 167,171,172

[56] References Cited UNITED STATES PATENTS 11/1928 Round l79/1l5.5 R 2/1930 Barton 179/1 15.5 R

1,966,564 I 7/1934 Schlenker l79/ll5.5 VC 3,518,460 6/1970 Wood et al. 310/86 FOREIGN PATENTS OR APPLICATIONS 607,594 9/1948 Great Britain 179/1 15.5 R

Primary Examiner-William C. Cooper Assistant Examiner-George G. Stellar Attorney, Agent, 0r Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT The suspension wires extending tangentially to the outer periphery of the coil bobbin positioned within a cylindrical air gap of the magnetic circuit of a loudspeaker defined by the magnetic plate forming a portion of that circuit and the pole, include an integral wire coil portion permitting expansion and contraction in the direction of the wire axis. A viscous damper may be applied to the wire adjacent the coil intermediate the coil and the bobbin and may bridge the wire and the fixed magnetic plate.

5 Claims, 4 Drawing Figures 1. EX'PANDABLE SUSPENSION SYSTEM FOR LOUDSPEAKER BOBBIN CROSS REFERENCES TO RELATED APPLICATIONS AND PATENTS The subject matter of this application has reference to the subject matter of application Ser. No. 370,189 filed June 14, 1973, entitled Vibration Dampening Mounting System For Wire Suspended Loudspeaker Bobbin, and assigned to the common assignee, and US. Pat. Nos. 3,819,876 and 3,828,l44.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to loudspeakers of the type wherein a voice coil bobbin having a voice coil wound about the bobbin periphery is disposed within a cylindrical air gap formed within the magnetic circuit, and more particularly, to such a loudspeaker, where a plurality of suspension wires extend tangentially to the periphery of the bobbin and couple the bobbin periphery to a fixedsupport on a stationary element of the magnetic circuit.

2. Description of the Prior Art In loudspeakers of this type, conventionally a plurality of suspension wires are distributed circumferentially and extend in a tangential direction relative to the outer periphery of the bobbin and are fixed at one end to the bobbin, at the other end to a stationary member forming a part of the magnetic circuit. In loudspeakers where the bobbin is supported by suspension wires in this manner, the sound characteristics have great merit in comparison with loudspeakers using suspension arrangement of different types. However, when the bobbin vibrates along its axis in accordance with an electrical current signal applied to the voice coil,it is so inclined that the bobbin rotates about its axis. This is caused by the fact that the coupling point between the suspension wires and the bobbin move relative to the vibrating direction in proportion to the amount of vibration of the bobbin. Further, this rotary power acting on the bobbin acts in terms of compression or expansion between the neighboring coupling points, with the result that the bobbin resonates on its circumference, and to make matters worse, the bobbin and the diaphragm coupled thereto are transformed. Such rotation and transformation have adverse effects on the sound characteristics of the loudspeaker in addition to the resonation of the suspension wires themselves.

It is therefore an object of the present invention to provide a loudspeaker in terms of an improved structure which diminishes the rotary vibration of the bobbin caused by the vibration of the diaphragm and resonation between the bobbin and the suspension wires.

SUMMARY OF THE INVENTION The present invention is directed to a loudspeaker which employs a cylindrical bobbin having a voice coil wound about its periphery and disposed within a cylindrical air gap of the magnetic circuit by means ofa plurality of suspension wires which extend tangentially to the outer periphery of the bobbin and are fixed at one end to theperiphery of the bobbin and at the other end to a fixed magnetic plate forming a part of the magnetic circuit. In such a loudspeaker, the improvement comprises means carried by the wire to permit the wires to expand and contract in the direction of the wire axis, preferably the means comprises an integral wire coil portion intermediate of the ends of the wires. Further. the wires may include a viscous damping material which may surround the wire at a pointadjacent the in tegral coil and bridge the gap between the wire and the stationary plate, the viscous material preferably may be located on the wire intermediate of the integral wire coil portion and the end of the wire attached to the bobbin.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, partially cut away, of a loudspeaker incorporating the wire suspension means of .the' present invention in one form.

FIG. 2 is a sectional, elevational view of a portion of the loudspeaker of FIG. 1.

FIG. 3 is a sectional, elevational view of a loudspeaker incorporating a wire suspension arrangement of the invention in alternate form.

FIG. 4 is a sectional, elevational view of a portion of a loudspeaker incorporating the wire suspension system of the present invention in yet another form.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In explaining one embodiment of the present invention in accordance with the drawings, and in particular, FIGS. 1 and 2, an annular magnet l is secured on one end face to a discal yoke 2 and on the other end face has secured thereto an annular plate 3, these elements forming along with pole 4 the stationary elements of the magnetic circuit. The pole 4 is columnar, and is secured on the yoke 2 so as to provide an annular gap of predetermined width between the peripheral surface of the pole 4 and the inner periphery of plate 3, thus completing the magnetic circuit.

A cylindrical voice coil bobbin 6 is disposed in centric fashion about the upper end of columnar pole 4 and forms a cylindrical assembly with voice coil 5 which is wound about the outer periphery of the bobbin 6, the assembly having an inner diameter slightly larger than the diameter of pole 4 and an outer diameter slightly smaller than the diameter of the inner periphery of plate 3 and is disposed within the air gap so as to be movable freely in an axial direction. The bobbin 6 is provided with a domed shape diaphragm 7 which overlies that end of bobbin 6 facing away from pole 4.

Further, on the upper surface of plate 3, there are secured at circumferentially spaced positions a plurality of flanges or mounting posts. The flanges are distributed and positioned respectively on the circumference of a circle which is concentric with respect to the axis of the pole with certain spacing between the flanges with one end ofa like number of suspension wires being secured respectively thereto.

Each suspension wire extends in a tangential direction relative to the outer periphery of bobbin 6 such that the inner end of each suspension wire is secured respectively to the outer periphery of bobbin 6 through a suitable connecting member 10 at spaced circumferential positions corresponding to the flanges but circumferentially offset therefrom. Further, each suspension wire 9 is made of a material having high resiliency such as beryllium-copper alloy and each wire is provided with an integral coil portion or coil 9 preferably near the outer end of the wire, that is, the end fixed to flange or post 8. The integral coil portion 9., permits the wire to bend at this point in addition to bending elsewhere due to its high resiliency, but also the wire is able to expand and contract in the direction of the axis of the wire due to the elasticity of the coil portion or integral coil 9a.

In the loudspeaker as constructed above, when a signal current is applied to the voice coil 5, the power tends to move it in an axialdirection, and in which case, the suspension wire 9 causes the bobbin 6 to move parallel to the axis thereof, owing to the bending and expanding and contracting of the wire. Consequently, there is no deterioration in the sound characteristics of the loudspeaker due to the rotation of bobbin 6, and a further result, little deformation or transformation of the bobbin 6 due to the compression and expansion normally occur as a result of the rotative' power acting on such a bobbin.

In the embodiment of FIGS. 1 and 2, the coil portion or integral coil 9,, is so formed that the suspension wire 9 may expand and contract. However, coil portion 9,, may have substituted therefor, a portion which is loop shaped, or N-shaped in configuration to provide the spring resilience necessary to permit expansion and contraction along the axis of the remaining wire portion.

Turning to FIG. 3, each suspension wire 9, and wherein, like elements are given like numerical designations, the arrangement is identical to that of FIGS. 1 and 2 with the exception that the suspension wire is provided at a portion immediately adjacent the integral wire coil portion 9,, and to the side of that coil facing the bobbin, with a layer 11 of viscous resilient material such that the mass of viscous material completely surrounds the wire, the effect of the viscous material is to effectively absorb vibration of the suspension wire 9, so there results little deterioration of the frequency and transient characteristics which would normally result from resonance of the suspension wire 9.

Further, in FIG. 4, wherein again like elements are given like numerical designations, the viscous resilient material lla not only surrounds the wire 9 adjacent the coil portion 9,, of the wire, but actually bridges the gap between the wire 9 at this point, and fixed plate 3 of the magnetic circuit, the effect of the viscous material or damper 11a is to provide a similar damping effect in terms of the resonance of the suspension wire 9 in the same manner as the embodiment of FIG. 3.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other charges in form and details may be made therein without departing from the spirit. and scope, of the invention.

What is claimed is:

l. A loudspeaker including a cylindrical bobbin having a voice coil wound about its periphery and being suspended within a cylindrical air gap of the loudspeaker magnetic circuit which includes a fixed magnetic member, by means of a plurality of suspension wires which extend tangentially in the same direction from the outer periphery of the bobbin at equally spaced circumferential positions to the fixed magnetic member and are fixed at one end to the bobbin and at the opposite end to the fixed magnetic member, the improvement comprising: an integral, wire coil portion intermediate the ends of each wire and aligned coaxially therewith to permit the wires to expand and contract in the direction of the wire axis to diminish rotary oscillation of the bobbin during energization of the voice coil, but permitting the wire coil portion to bend along with the remaining portion of each wire to permit axial movement of the bobbin with respect to the fixed magnetic member.

2. The loudspeaker as claimed in claim 1, wherein each suspension wire further includes viscous damping means operatively associated therewith.

3. The loudspeaker as claimed in claim 2, wherein said viscous damping means comprises a mass of viscous damping material fixed to each wire and said fixed magnetic member and bridging the gap between the wires and said fixed magnetic member and positioned to the side of said unitary, integral wire coil portion closest to said bobbin.

4. The loudspeaker as claimed in claim 2, wherein said viscous damping means comprises a mass of viscous damping material surrounding each wire and supported thereby.

5. The loudspeaker as claimed in claim 4, wherein said mass of viscous damping material is positioned adjacent to the integral wire coil portion and intermediate said wire coil portion and said bobbin. 

1. A loudspeaker including a cylindrical bobbin having a voice coil wound about its periphery and being suspended within a cylindrical air gap of the loudspeaker magnetic circuit which includes a fixed magnetic member, by means of a plurality of suspension wires which extend tangentially in the same direction from the outer periphery of the bobbin at equally spaced circumferential positions to the fixed magnetic member and are fixed at one end to the bobbin and at the opposite end to the fixed magnetic member, the improvement comprising: an integral, wire coil portion intermediate the ends of each wire and aligned coaxially therewith to permit the wires to expand and contract in the direction of the wire axis to diminish rotary oscillation of the bobbin during energization of the voice coil, but permitting the wire coil portion to bend along with the remaining portion of each wire to permit axial movement of the bobbin with respect to the fixed magnetic member.
 1. A loudspeaker including a cylindrical bobbin having a voice coil wound about its periphery and being suspended within a cylindrical air gap of the loudspeaker magnetic circuit which includes a fixed magnetic member, by means of a plurality of suspension wires which extend tangentially in the same direction from the outer periphery of the bobbin at equally spaced circumferential positions to the fixed magnetic member and are fixed at one end to the bobbin and at the opposite end to the fixed magnetic member, the improvement comprising: an integral, wire coil portion intermediate the ends of each wire and aligned coaxially therewith to permit the wires to expand and contract in the direction of the wire axis to diminish rotary oscillation of the bobbin during energization of the voice coil, but permitting the wire coil portion to bend along with the remaining portion of each wire to permit axial movement of the bobbin with respect to the fixed magnetic member.
 2. The loudspeaker as claimed in claim 1, wherein each suspension wire further includes viscous damping means operatively associated therewith.
 3. The loudspeaker as claimed in claim 2, wherein said viscous damping means comprises a mass of viscous damping material fixed to each wire and said fixed magnetic member and bridging the gap between the wires and said fixed magnetic member and positioned to the side of said unitary, integral wire coil portion closest to said bobbin.
 4. The loudspeaker as claimed in claim 2, wherein said viscous damping mEans comprises a mass of viscous damping material surrounding each wire and supported thereby. 